just in the process of putting my 87 KX 250 back together, it needs patience, a manual, some mechanical dexterity, a good friend who is mechanically good to make you pause before you do a mad thing. The difficult tasks just require you to think about things a little
I am doing it so I know what to do in the future.
I made all the tools for pulling apart and pulling together using steel bars, 2 inch steel tube and threaded rod. Getting the crank in, requires a freezer and a partner who does not mind you using the oven for half an hour.
I can email you the pics of the pulling tools I made. I would buy the clymer manual before you start. It will be the best $30 you spend.
Once it is all done, I will setup a website. Look up Rocky Mountain ATV on you tube, it shows you the basics.
The other option is to pay the local dealer to do it but arrange so you can assist and observe.
Anyway, that is my view, good luck.